The invention relates to a micro-mixer having at least one mixing point which is connected to an inlet channel arrangement having at least two inlet channels and to an outlet channel arrangement. The invention relates furthermore to a mixing method for at least two fluids which are supplied from different directions.
Mixing of fluids is frequently required in order to initiate a chemical reaction. Such chemical reactions are necessary, for example, in an analysis in which the presence and/or concentration of a species in a fluid is to be determined. For that purpose the fluid has added to it a reagent (or several reagents), which form with the species a reaction product which can be detected in a detector. A controlled and homogeneous mixing of the fluid and the reagent, that is, between two or more fluids, is desirable here. The volume required for the mixing should be kept as small as possible, however, in order that the consumption of reagents does not become too great.
A static micro-mixer of the kind mentioned in the introduction has been proposed by the Technischer Universitat Ilmenau, Faculty of Engineering, micro-systems engineering department in D-98684 Ilmenau. The base body of this micro-mixer consists of silicon. Micro-channels and openings are made in this base body. These channels are hermetically sealed by silicon or glass substrates. Mixing of two liquids is effected in that these two liquids are layered horizontally side by side in a mixing element and then separated vertically. The mixing element is in this case formed by a recess into which the two inlet channels open from opposite sides. Two part-flows are then extracted from this recess and are later mixed in the same manner in a following mixing element.
With this construction it is relatively difficult to predict the mixing behaviour of the liquids with sufficient accuracy. Predictions about the course of the reaction between the two fluids are therefore possible only to a limited extent. In a subsequent analysis of a reaction product there is therefore always the uncertainty as to whether the reaction, after complete mixing of the two fluids, has already finished or, if that is not the case, whether the individual reaction times are reproducible. This disadvantage can, of course, be mitigated by waiting for a certain time after bringing the two fluids together, but this waiting time slows down the analysis.